IIRC limit isn't the copper, it's the CO interconnects with high/low frequency cutoffs, the same copper was used for 1.5Mbps synchronous DSL. For very short run

IIRC limit isn't the copper, it's the CO interconnects with high/low frequency cutoffs, the same copper was used for 1.5Mbps synchronous DSL. For very short runs, 50Mbps VDSL